U.S. patent number 8,756,776 [Application Number 12/579,263] was granted by the patent office on 2014-06-24 for method for manufacturing a disk drive microactuator that includes a piezoelectric element and a peripheral encapsulation layer.
This patent grant is currently assigned to Western Digital Technologies, Inc.. The grantee listed for this patent is Yih-Jen D. Chen, Robert J. McNab. Invention is credited to Yih-Jen D. Chen, Robert J. McNab.
United States Patent |
8,756,776 |
Chen , et al. |
June 24, 2014 |
Method for manufacturing a disk drive microactuator that includes a
piezoelectric element and a peripheral encapsulation layer
Abstract
A method of manufacturing a microactuator. The method includes
providing a sheet of a piezoelectric material having an
electrically conductive layer on at least one side of the sheet.
The method includes cutting the sheet to form a plurality of
piezoelectric elements. Each of the piezoelectric elements includes
a first element side with an electrically conductive layer. Each
first element side includes a peripheral portion and an exposed
portion interior to the peripheral portion. The method includes
forming an encapsulation layer over the peripheral portion and not
over the exposed portion of at least one of the sides. The
encapsulation layer comprises a material of lesser electrical
conductivity than the electrically conductive layer. An apparatus
for manufacturing the microactuators may also be provided that
includes a first fixture and first and second alignment combs.
Inventors: |
Chen; Yih-Jen D. (Fremont,
CA), McNab; Robert J. (San Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Chen; Yih-Jen D.
McNab; Robert J. |
Fremont
San Jose |
CA
CA |
US
US |
|
|
Assignee: |
Western Digital Technologies,
Inc. (Irvine, CA)
|
Family
ID: |
50943900 |
Appl.
No.: |
12/579,263 |
Filed: |
October 14, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
11298368 |
Dec 9, 2005 |
|
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|
Current U.S.
Class: |
29/25.35; 29/846;
29/841; 360/291.9; 29/603.03; 360/294.4 |
Current CPC
Class: |
G11B
5/4873 (20130101); G11B 5/483 (20150901); G11B
5/4826 (20130101); H01L 41/253 (20130101); H01L
41/053 (20130101); H01L 41/23 (20130101); H01L
41/338 (20130101); H01L 41/0533 (20130101); H01L
41/0986 (20130101); H01L 41/25 (20130101); H02N
2/22 (20130101); Y10T 29/49025 (20150115); H02N
1/008 (20130101); Y10T 29/49155 (20150115); Y10T
29/42 (20150115); Y10T 29/49146 (20150115) |
Current International
Class: |
G11B
5/84 (20060101); H01L 41/22 (20130101) |
Field of
Search: |
;29/25.35,603.03,603.04,841,842,846 ;360/291.9,294.4,292
;73/514.34 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
English Language Translation of Japanese Patent Publication
(Certified), JP 63-60617, Jun. 2013. cited by examiner .
Office Action dated May 7, 2008 from U.S. Appl. No. 11/298,368,
filed Dec. 9, 2005, 7 pages. cited by applicant .
Office Action dated Sep. 9, 2008 from U.S. Appl. No. 11/298,368,
filed Dec. 9, 2005, 9 pages. cited by applicant .
Office Action dated Feb. 9, 2009 from U.S. Appl. No. 11/298,368,
filed Dec. 9, 2005, 5 pages. cited by applicant .
Office Action dated Feb. 10, 2009 from U.S. Appl. No. 11/298,368,
filed Dec. 9, 2005, 6 pages. cited by applicant .
Office Action dated Jul. 16, 2009 from U.S. Appl. No. 11/298,368,
filed Dec. 9, 2005, 15 pgaes. cited by applicant .
Monk, David J., et al., "Media Compatible Packaging and
Environmental Testing of Barrier Coating Encapsulated Silicon
Pressure Sensors", Solid-State Sensor and Actuator Workshop, Hilton
Head, South Carolina, Jun. 2-6, pp. 36-41, 1996. cited by applicant
.
Monk, David J., "Thin Film Organic Passivation Coatings for Media
Compatible Pressure Sensors", Motorola Inc. Technical Developments,
pp. 29-30, Jul. 1995. cited by applicant .
Bitko, Gordon, "Annealing Thin Film Parylene Coatings for Media
Compatible Pressure Sensors", Motorola Inc. Technical Developments,
pp. 92-94, Aug. 1996. cited by applicant.
|
Primary Examiner: Tugbang; A. Dexter
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application claims priority under 35 U.S.C. section 121
as a divisional of pending U.S. patent application Ser. No.
11/298,368, entitled "METHOD FOR MANUFACTURING A DISK DRIVE
MICROACTUATOR THAT INCLUDES A PIEZOELECTRIC ELEMENT AND A
PERIPHERAL ENCAPSULATION LAYER" and filed on Dec. 9, 2005, which is
hereby incorporated by reference herein in its entirety.
Claims
We claim:
1. A method of manufacturing microactuators for use in a disk
drive, the method comprising the acts of: (a) providing a sheet of
a piezoelectric material having a first electrically conductive
layer on a first side of the sheet; (b) cutting the sheet to form a
plurality of piezoelectric elements, each of the piezoelectric
elements including a first element side with a portion of the first
electrically conductive layer, each first element side including a
peripheral portion and an exposed portion disposed interior to the
peripheral portion; and (c) forming an encapsulation layer over the
peripheral portion and not over the exposed portion of at least one
of the first element sides, the encapsulation layer comprising a
material of lesser electrical conductivity than the first
electrically conductive layer, wherein the act of forming includes
(i) providing a first fixture including a fixture base and a
plurality of protrusions extending from the fixture base, each
protrusion including a distal support surface that is approximately
the same size as an exposed portion of a respective one of the
first element sides; and (ii) positioning each of the piezoelectric
elements upon a respective distal support surface of the first
fixture with the respective exposed portion of a respective first
element side upon the distal support surface; wherein the act of
positioning includes using a first alignment comb to position the
piezoelectric elements with respect to the first fixture, the first
alignment comb including a plurality of first tines, the
piezoelectric elements being positioned between respective ones of
the first tines.
2. The method of claim 1 wherein the act of positioning further
includes using a second alignment comb to position the
piezoelectric elements with respect to the first fixture, the
second alignment comb including a plurality of second tines, the
piezoelectric elements being positioned between respective ones of
the second tines, the second tines being oriented approximately
orthogonally relative to the first tines.
3. A method of manufacturing microactuators for use in a disk
drive, the method comprising the acts of: (a) providing a sheet of
a piezoelectric material having a first electrically conductive
layer on a first side of the sheet; (b) cutting the sheet to form a
plurality of piezoelectric elements, each of the piezoelectric
elements including a first element side with a portion of the first
electrically conductive layer, each first element side including a
peripheral portion and an exposed portion disposed interior to the
peripheral portion; and (c) forming an encapsulation layer over the
peripheral portion and not over the exposed portion of at least one
of the first element sides, the encapsulation layer comprising a
material of lesser electrical conductivity than the first
electrically conductive layer, wherein the act of forming includes
(i) providing a first fixture including a fixture base and a
plurality of protrusions extending from the fixture base, each
protrusion including a distal support surface that is approximately
the same size as an exposed portion of a respective one of the
first element sides; and (ii) positioning each of the piezoelectric
elements upon a respective distal support surface of the first
fixture with the respective exposed portion of a respective first
element side upon the distal support surface; (iii) providing a
second fixture including a fixture base and a plurality of
protrusions extending from the fixture base, each protrusion
including a distal support surface that is approximately the same
size as an exposed portion of a respective one of the second
element sides, and positioning each of the piezoelectric elements
upon a respective distal support surface of the second fixture with
the respective exposed portion of a respective second element side
upon the distal support surface; and iv) using a first alignment
comb to position the piezoelectric elements with respect to the
second fixture, the first alignment comb including a plurality of
first tines, the piezoelectric elements being positioned between
respective ones of the first tines.
4. The method of claim 3 further comprising using a second
alignment comb to position the piezoelectric elements with respect
to the second fixture, the second alignment comb including a
plurality of second tines, the piezoelectric elements being
positioned between respective ones of the second tines, the second
tines being oriented approximately orthogonally relative to the
first tines.
5. The method of claim 4 further comprising affixing the first and
second fixtures relative to each other and subsequently removing
the first and second alignment combs, the act of forming occurring
while the piezoelectric elements are positioned between the affixed
first and second fixtures.
Description
FIELD OF THE INVENTION
The present invention relates generally to disk drives, and in
particular to a method and apparatus for manufacturing a disk drive
microactuator that includes a piezoelectric element and a
peripheral encapsulation layer.
BACKGROUND
The typical hard disk drive includes a head disk assembly (HDA) and
a printed circuit board assembly (PCBA) attached to a disk drive
base of the HDA. The head disk assembly includes at least one disk
(such as a magnetic disk), a spindle motor for rotating the disk,
and a head stack assembly (HSA). The printed circuit board assembly
includes a servo control system in the form of a disk controller
for generating servo control signals. The head stack assembly
includes at least one head, typically several, for reading and
writing data from and to the disk. The head stack assembly is
controllably positioned in response to the generated servo control
signals from the disk controller. In so doing, the attached heads
are moved relative to tracks disposed upon the disk.
The head stack assembly includes an actuator assembly, at least one
head gimbal assembly, and a flex circuit assembly. A conventional
"rotary" or "swing-type" actuator assembly typically includes a
rotary actuator having an actuator body. The actuator body has a
pivot bearing cartridge to facilitate rotational movement of the
actuator assembly. An actuator coil is supported by the actuator
body and is configured to interact with one or more magnets,
typically a pair, to form a voice coil motor. One or more actuator
arms extend from an opposite side of the actuator body.
The spindle motor typically includes a rotatable spindle motor hub,
a magnet attached to the spindle motor hub, and a stator. The
stator typically includes a series of coils that are in electrical
communication with the printed circuit board assembly. With this
general configuration, the various coils of the stator are
selectively energized to form an electromagnetic field that
pulls/pushes on the magnet, thereby imparting a rotational motion
onto the spindle motor hub. Rotation of the spindle motor hub
results in the rotation of the attached disks.
A topic of concern is the controlled positioning of the heads in
relation to tracks of the disks. The pivoting motion of the rotary
actuator provides a basic mode of actuation of positioning the
heads. Prior art attempts have been directed towards providing a
secondary actuation of the heads, for example to increase bandwidth
or track-following resolution. Such a configuration has been
referred to a dual-stage actuation or microactuation. It is
contemplated that there is need in the art for an improved
microactuator configuration and the various methodologies for
fabricating the related components.
SUMMARY
A method of manufacturing microactuators for use in a disk drive is
provided. The method includes providing a sheet of a piezoelectric
material having an electrically conductive layer on at least one
side of the sheet. The method further includes cutting the sheet to
form a plurality of piezoelectric elements. Each of the
piezoelectric elements includes a first element side with an
electrically conductive layer. Each first element side includes a
peripheral portion and an exposed portion disposed interior to the
peripheral portion. The method further includes forming an
encapsulation layer over the peripheral portion and not over the
exposed portion of at least one of the first element sides. The
encapsulation layer comprises a material of lesser electrical
conductivity than the electrically conductive layer.
According to another aspect of the present invention, there is
provided an apparatus for manufacturing a plurality of
piezoelectric microactuators each for use in a disk drive. The
apparatus includes a first fixture including a fixture base and a
plurality of protrusions extending from the fixture base. Each
protrusion includes a distal support surface that is approximately
the same size as an exposed portion of a first side of a
piezoelectric element. The apparatus further includes a first
alignment comb including a plurality of first tines. The first
tines are spaced to position the piezoelectric element between
respective ones of the first tines. The apparatus further includes
a second alignment comb including a plurality of second tines. The
second tines are spaced to position the piezoelectric element
between respective ones of the second tines. The second tines are
oriented approximately orthogonally relative to the first
tines.
According to another aspect of the present invention, there is
provided a microactuator for use in a disk drive. The microactuator
includes a piezoelectric element defining a first element side. The
first element side includes a first peripheral portion and a first
exposed portion disposed interior to the first peripheral portion.
The microactuator further includes a first electrically conductive
layer disposed upon the first peripheral portion and the first
exposed portion. The microactuator further includes an
encapsulation layer disposed over the first peripheral portion and
not over the first exposed portion. The encapsulation layer
comprises a material of lesser electrical conductivity than the
electrically conductive layer.
According to yet another embodiment of the present invention, there
is provided a disk drive. The disk drive includes a disk drive
base, a spindle motor coupled to the disk drive base, a coarse
actuator rotatably coupled to the disk drive base, and a
microactuator coupled to the coarse actuator. The microactuator is
as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded top perspective view of a disk drive;
FIG. 2 is a bottom plan view of a portion of a head stack assembly
including a pair of microactuators;
FIG. 3 is a perspective top view of the portion of the head stack
assembly of FIG. 2;
FIG. 4 is a perspective view of a sheet of piezoelectric
material;
FIG. 5 is a perspective view of the sheet of piezoelectric material
of FIG. 4 with an electrically conductive layer;
FIG. 6 is a perspective view of the sheet of FIG. 5 with intended
cut-lines shown;
FIG. 7 is a perspective view of a piezoelectric element;
FIG. 8 is a perspective view of a first fixture;
FIG. 9 is a perspective view of the first fixture of FIG. 8 with a
first alignment comb;
FIG. 10 is a perspective view of the first fixture and first
alignment comb of FIG. 9 with piezoelectric elements;
FIG. 11 is a cross-sectional view of the first fixture, the first
alignment comb, and piezoelectric elements as seen along axis 11-11
of FIG. 10;
FIG. 12 is a perspective view of the first fixture, the first
alignment comb, and the piezoelectric elements of FIG. 10 with a
second alignment comb;
FIG. 13 is a cross-sectional view of the first fixture, the second
alignment comb, and piezoelectric elements as seen along axis 13-13
of FIG. 12;
FIG. 14 is a perspective view of the first fixture, the first
alignment comb, the piezoelectric elements, and the second
alignment comb of FIG. 10 with a second fixture;
FIG. 15 is the perspective view of FIG. 10 with the second fixture
positioned atop the first fixture;
FIG. 16 is the perspective view of FIG. 15 with clamps;
FIG. 17 is the perspective view of FIG. 16 with the first and
second alignment combs exploded away from the first and second
fixtures;
FIG. 18 is a cross-sectional view of the first fixture,
piezoelectric elements, and the second fixture as seen along axis
18-18 of FIG. 17;
FIG. 19 is the first fixture, the piezoelectric elements, the
second fixture, and the clamps of FIGS. 17 and 18 as seen from
another perspective view;
FIG. 20 is a cross-sectional view similar to the view of FIG. 18,
however, with the piezoelectric elements having an encapsulation
layer;
FIG. 21 is a top plan view of a microactuator;
FIG. 22 is an enlarged portion of the top plan view of the
microactuator of FIG. 21;
FIG. 23 is top perspective view of the microactuator of FIG.
21;
FIG. 24 is an enlarged portion of the top perspective view of the
microactuator of FIG. 23; and
FIG. 25 is a bottom perspective view of the microactuator of FIG.
21.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is depicted an exploded perspective
view of a disk drive 10 capable of incorporating an embodiment of
the present invention (details of which are discussed below and
shown in additional figures). The disk drive 10 includes a head
disk assembly (HDA) 12 and a printed circuit board assembly (PCBA)
14. The head disk assembly 12 includes a disk drive housing having
disk drive housing members, such as a disk drive base 16 and a
cover 18. The disk drive base 16 and the cover 18 collectively
house disks 20, 22. A single disk or additional disks may be
utilized. The disks 20, 22 each include a disk inner diameter, and
a plurality of tracks for storing data. The disks 20, 22 may be of
a magnetic recording type of storage device, however, other
arrangements such as optical recording may be utilized. The head
disk assembly 12 further includes a spindle motor 24 for rotating
the disks 20, 22 about a disk rotation axis 26. The head disk
assembly 12 further includes a head stack assembly 28 rotatably
attached to the disk drive base 16 in operable communication with
the disks 20, 22. The head stack assembly 28 includes a rotary
actuator 30. The rotary actuator 30 may be considered a course
actuator.
The rotary actuator 30 includes an actuator body 32 and actuator
arms 34 that extend from the actuator body 32. Distally attached to
the actuator arms 34 are suspension assemblies 36 (for ease of
illustration only the topmost actuator arm and suspension assembly
are denoted). The suspension assemblies 36 respectively support
heads 38. The suspension assemblies 36 with the heads 38 are
referred to as head gimbal assemblies. It is contemplated that the
number of actuator arms and suspension assemblies may vary
depending upon the number of disks and disk surfaces utilized.
Each head 38 typically includes a transducer for writing and
reading data. Each transducer typically includes a writer and a
read element. In magnetic recording applications, the transducer's
writer may be of a longitudinal or perpendicular design, and the
read element of the transducer may be inductive or
magnetoresistive. In optical and magneto-optical recording
applications, the head 38 may also include an objective lens and an
active or passive mechanism for controlling the separation of the
objective lens from a disk surface of the disks 20, 22. Each of the
disks 20, 22 includes opposing disk surfaces. In magnetic recording
applications the disk surface typically includes one or more
magnetic layers. Data may be recorded along data annular regions on
a single disk surface or both.
The head stack assembly 28 may be pivoted such that each head 38 is
disposed adjacent to the various data annular regions from adjacent
the outer diameter to adjacent the inner diameter of each of the
disks 20, 22. In the embodiment shown, the actuator body 32
includes a bore, and the rotary actuator 30 further includes a
pivot bearing cartridge engaged within the bore for facilitating
the actuator body 32 to rotate between limited positions about an
axis of rotation 40. The rotary actuator 30 further includes a coil
support 42 that extends from one side of the actuator body 32
opposite the actuator arms 34. The coil support 42 is configured to
support an actuator coil 44.
First and second magnets 46, 48 are supported by magnet supports
50, 52 which are attached to the disk drive base 16 (the first
magnet 46 is denoted in dashed lining and it is understood that it
is disposed at an underside of the magnet support 50). The actuator
coil 44 interacts with the first and second magnets 46, 48 to form
a voice coil motor for controllably rotating the actuator 30. The
head stack assembly 28 further includes a flex cable assembly 54
and a cable connector 57. The cable connector 57 is attached to the
disk drive base 16 and is disposed in electrical communication with
the printed circuit board 14. The flex cable assembly 54 supplies
current to the actuator coil 44 and carries signals between the
heads and the printed circuit board assembly 14.
Referring now to FIGS. 2 and 3 there is depicted enlarged views of
a portion of the suspension 36. In the embodiment shown, the
suspension 36 includes a swage plate 56. The swage plate 56 is
attached to the actuator arm 34. A load beam 58 is distally
attached to the swage plate 56. A flex circuit assembly 55 extends
along the swage plate 56 and the load beam 58. The flex circuit
assembly 55 is electrically connected to the flex cable assembly
54. The head 38 may be attached to and electrically connected to
the flex circuit assembly 55 at the load beam 58. In the particular
embodiment shown, there are provided microactuators 60, 62 that are
configured to move the head 38 relative to the actuator body 32.
The microactuators 60, 62 may be used to move the head 38 relative
to a longitudinal axis 64 extending radially from the axis of
rotation 40 along the actuator arm 34 and along the swage plate 56.
Arrow indicators are shown to indicate direction of movement of the
head 38 due to actuation of the microactuators 60, 62. As such, the
microactuators 60, 62 may be utilized to "fine tune" controlled
movement of the head 38 in comparison the course adjustments
facilitated by the overall rotation of the rotary actuator 30 about
the axis of rotation 40. To accomplish such "fine tuning" the
microactuators 60, 62 may have greater bandwidth, but lesser
stroke, than the voice coil motor. The microactuators 60, 62 are
discussed in detail below and the microactuator 60 shown in further
detail in FIGS. 21-25.
The microactuators 60, 62 may be electrically connected to the flex
circuit assembly 55. The flex circuit assembly 55 may include a
plurality of traces 66 that are electrically connected to the head
36. The traces 66 may be disposed upon a dielectric layer
comprising a nonconductive material. The flex circuit assembly 55
may further include microactuator traces 68, 70 that are
electrically connected to the microactuators 60, 62. The flex
circuit assembly 55 may include a tab portion 94 that extends from
a main portion 96 of the flex circuit assembly 55. The
microactuator traces 68, 70 may extend along the tab portion
94.
While in the embodiment shown there are two such microactuators 60,
62 shown, it is contemplated that only a single microactuator may
be utilized, as well as more than two microactuators may be
utilized. Moreover, while in the embodiment shown the
microactuators 60, 62 are disposed between the swage plate 56 and
the load beam 58, the microactuators 60, 62 may be utilized at
other locations about the rotary actuator 30. For example, it is
contemplated that microactuators may be positioned and used in a
load beam to facilitate relative movement between different
portions of such load beam. As another example, it is contemplated
that the microactuators may be positioned and used in an actuator
arm to facilitate relative movement between different portions of
such actuator arm.
According to an embodiment as shown, there is provided the disk
drive 10. The disk drive 10 includes the disk drive base 16. The
disk drive 10 further includes the spindle motor 24 coupled to the
disk drive base 16. The disk drive 10 includes a coarse actuator,
such as the rotary actuator 30 that is rotatably coupled to the
disk drive base 16. The disk drive further includes a
microactuator, such as the microactuator 60 that is coupled to the
rotary actuator 30. Referring additionally to FIGS. 21-25, there is
depicted an enlarged view of the microactuator 60. The
microactuator 60 includes a piezoelectric element 72 defining a
first element side 74. The first element side 74 includes a first
peripheral portion 76 and a first exposed portion 78 disposed
interior to the first peripheral portion 76. The microactuator 60
further includes a first electrically conductive layer 80 disposed
upon the first peripheral portion 76 and the first exposed portion
78. The microactuator 60 further includes an encapsulation layer 82
disposed over the first peripheral portion 76 and not over the
first exposed portion 78. The encapsulation layer 82 comprises a
material of lesser electrical conductivity than the electrically
conductive layer 80.
According to various embodiments, the piezoelectric element 72
further defines a second element side 84 opposite the first element
side 74 as illustrated in FIG. 25. The second element side 84 may
include a second peripheral portion 86 and a second exposed portion
88 disposed interior to the second peripheral portion 86. A second
electrically conductive layer 90 may be disposed upon the second
peripheral portion 86 and the second exposed portion 88. The
encapsulation layer 82 may be further disposed over the second
peripheral portion 86 and not the second exposed portion 88. In
this regard, the piezoelectric element 72 may further include
lateral element sides 92 disposed between the first and second
element sides 74, 84. In the embodiment shown, the encapsulation
layer 82 extends upon the first peripheral portion 76, the lateral
element sides 92, and the second peripheral portion 86.
In the embodiment shown, the microactuators 60, 62 are electrically
connected to the microactuator traces 68, 70 at the first element
side 74 via the first electrically conductive layer 80. It is
contemplated that the second electrically conductive layer 90 need
not be electrically connected to any of the traces, such as shown.
However, the second electrically conductive layer 90 could be
electrically connected to additional traces in order to establish a
voltage potential across the piezoelectric element 72 for actuation
of the microactuators 60, 62. The first and second electrically
conductive layers 80, 90 comprise electrically conductive material.
Suitable materials include metals, such as gold and copper.
The piezoelectric element 72 exhibits a change in physical geometry
in response to the application of a voltage potential across at
least a portion of such piezoelectric element 72. Such change in
physical geometry includes expansion or contraction in specific
dimensions, as well as bending or twisting movements. The
piezoelectric element 72 may be formed of materials which may be
chosen from those which are well known to one of ordinary skill in
the art. An example of a suitable material used for the
piezoelectric element 72 is PZT (Lead Zirconate Titanate). The
piezoelectric element 72 may be generally rectangular shaped such
as shown. However, the piezoelectric element 72 may have other
shapes, including more complex geometries including those with
curvatures and/or non-uniform thicknesses.
In the embodiment shown, the piezoelectric elements 72 of the
microactuators 60, 62 are configured to expand and contract in a
lengthwise direction generally parallel to the longitudinal axis
64. By selectively energizing the microactuator traces 68, 70, the
piezoelectric elements 72 of the microactuators 60, 62 may be
actuated to expand and/or contract at differing times and
magnitude. This would result in the load beam 58 moving with
respect to the longitudinal axis 64 for controlled movement of the
attached head 38. Thus, a secondary or fine actuation may be
achieved relative to the primary or coarse actuation as implemented
by the pivoting movement of the rotary actuator 30 about the axis
of rotation 40.
By their nature suitable materials used to form the piezoelectric
element 72 have the potential to be a source of particle shedding.
Such particles are considered a contamination source within the
disk drive 10. As such, it is desirable to cover or otherwise coat
the piezoelectric element 72 with a material so as to mitigate such
particle shedding. In this regard, the outer surfaces of the
piezoelectric element 72 are coated with the first electrically
conductive layer 80 and the encapsulation layer 82. In the
particular embodiment shown, the second electrically conductive
layer 90 is further utilized for covering the piezoelectric element
72.
During the manufacture of the piezoelectric element 72 according to
the method as discussed below, a sheet of piezoelectric material is
provided that is repeatedly cut to form a multitude of
piezoelectric elements. It is contemplated that while in such sheet
form the entire sides of the sheet may be efficiently coated with
conductive material so as to form the first and second electrically
conductive layers 80, 90 of the yet to be formed piezoelectric
element 72. However, due to the nature of this manufacture process
the lateral sides of the various ones of the newly cut
piezoelectric elements are exposed piezoelectric material. It is
desirable to coat such lateral sides so as to encapsulate the
piezoelectric material.
An aspect of the present invention recognizes that merely coating
the lateral sides does not provide sufficient mitigation of
possible shedding of particles associated with the piezoelectric
material. This is because the coating of the lateral sides might
not completely coat the lateral sides as intended. In addition, due
to the inherent nature of the piezoelectric material changing its
geometry during actuation, repetitive actuation could result in an
opening of the "seam" at the lateral sides. This could allow for
the release of the particles of the piezoelectric material. As
such, the particular disposition of the encapsulation layer 82
being disposed over the first peripheral portion 76 and not over
the first exposed portion 78 ensure a degree of overlap so as to
comprehensively cover the piezoelectric material within at such
seam at the first element side 74. Likewise, the encapsulation
layer 82 may be further disposed over the second peripheral portion
86 and not over the second exposed portion 88 for overlapping
coverage at the second element side 84. As seen in FIG. 22, the
encapsulation layer 82 is disposed upon the lateral element sides
92 to a thickness "T." The thickness T may be between 1 and 1000
nanometers for example. In the horizontal direction of FIG. 22, the
encapsulation layer 82 overlaps the first electrically conductive
layer 80 by distance equal to the difference between the distance
"D" and the thickness "T." Examples of suitable materials for the
encapsulation layer 82 may include a polymeric material Parylene,
EGC-1700 under the trademark NOVEC manufactured by 3M Company, and
Z-Tetraol manufactured by Ausimont, a polymer under the trademark
ST-Poly manufactured by Achilles Corporation.
According to another aspect of the invention, there is provided the
disk drive 10. The disk drive 10 includes the disk drive base 16,
the spindle motor 24 coupled to the disk drive base 16, a coarse
actuator (such as the actuator 30) rotatably coupled to the disk
drive base 16, and a microactuator (such as microactuator 60)
coupled to the coarse actuator. The microactuator 60 is as
discussed above.
With reference to FIGS. 4-20, according to another embodiment of
the invention, there is provided a method of manufacturing
microactuators (such as the microactuator 60) for use in a disk
drive (such as disk drive 10). Referring to FIGS. 4 and 5, the
method includes an act of providing a sheet 98 of a piezoelectric
material having a first electrically conductive layer 104 on at
least one side of the sheet 100. FIG. 4 depicts the sheet 98 of
piezoelectric material. The sheet 96 includes a first sheet side
100 and an opposing second sheet side 102 (indicated in dashed line
as it is not seen in this view). FIG. 5 depicts the sheet 98 of
piezoelectric material with the first electrically conductive layer
104 on the first sheet side 100. Though not seen in this view, it
is contemplated that a second electrically conductive layer 106
(indicated in dashed line as it is not seen in this view) may be
disposed upon second sheet side 102 as well. The first and second
electrically conductive layers 104, 106 may be formed of any
electrically conductive material, such as a metal such as gold,
nickel or copper, in single or multiple layers. The first and
second electrically conductive layers 104, 106 may have a thickness
of 0.05 to 0.4 micrometers for example.
Referring now to FIG. 6 there is depicted the sheet 98 of
piezoelectric material of FIG. 5 as shown with a multitude of
intended cut-lines 108. The method further includes the act of
cutting the sheet 98 to form a plurality of piezoelectric elements.
A single piezoelectric element 72 is shown in FIG. 7 that would
correspond to such an element as produced as a result of the
cutting operation along the cut-lines 108. It is understood that
the arrangement of the cut-lines 108 dictate the resultant geometry
of the piezoelectric element 72. As described above, each of the
piezoelectric elements 72 includes the first element side 74 with
the first electrically conductive layer 80. Each of the
piezoelectric elements 72 includes a second element side 84
(indicated in dashed line as it is not seen in this view) opposite
the first element side 74. Each second element side 84 may include
the second electrically conductive layer 90 (indicated in dashed
line as it is not seen in this view).
As discussed above with reference to FIGS. 21-25, each first
element side 74 includes the first peripheral portion 76. Each
first element side further includes the first exposed portion 78
disposed interior to the first peripheral portion 76. Each second
element side 84 may include the second peripheral portion 86. Each
second element side may further include the second exposed portion
88 disposed interior to the second peripheral portion 86. The
method further includes the act of forming the encapsulation layer
82 over the first peripheral portion 76 and not over the first
exposed portion 78 of the first element side 74. As used herein,
the encapsulation layer 82 is used to refer to any material of
lesser electrical conductivity than the first electrically
conductive layer 80. The method may further include the act of
forming the encapsulation layer 82 over the second peripheral
portion 86 and not over the second exposed portion 88 of the second
element side 84. The encapsulation layer 82 comprises a material of
lesser electrical conductivity than the second electrically
conductive layer 90. In this regard, the encapsulation layer 82 may
have an electrical conductivity on the order of 1e-15 (1/Ohm*1/m)
for Parylene and 5e-10 (1/Ohm*1/m) for EGC-1700, for example. The
first and second electrically conductive layer 80, 90 may have an
electrical conductivity on the order of 49e6 (1/Ohm*1/m) for gold
and 15e6 (1/Ohm*1/m) for nickel. FIGS. 8-20 illustrate an
embodiment of the method that facilitates the application of the
encapsulation layer 82 upon the piezoelectric element 72 in the
context for manufacturing a plurality of microactuators 60.
Referring now to FIG. 8, the act of forming the encapsulation layer
82 may include providing a first fixture 110. The first fixture 110
includes a fixture base 112 and a plurality of protrusions 114
extending from the fixture base 112. Each protrusion 114 includes a
distal support surface 116. As will be seen in later figures and
discussed below, the distal support surface 116 is approximately
the same size as a first exposed portion 78 of a respective one of
the first element sides 74 of the various piezoelectric elements
72.
Referring now to FIG. 9, a first alignment comb 118 may be
provided. The first alignment comb 118 includes a plurality of
first tines 120. The first alignment comb 118 is positioned upon
the fixtures base 112 of the first fixture 110. The first tines 120
are aligned between various rows of the protrusions 114.
Referring to FIG. 10, the act of forming the encapsulation layer 82
may include positioning each of the piezoelectric elements 74 upon
a respective distal support surface 116 of the first fixture 110
with the respective first exposed portion 78 of a respective first
element side 74 upon the distal support surface 116. The act of
positioning may include using a first alignment comb 118 to
position the piezoelectric elements 74 with respect to the first
fixture 110. The piezoelectric elements 74 are positioned between
respective ones of the first tines 120.
FIG. 11 is a cross-sectional view as seen along axis 11-11 of FIG.
10. As can be seen, the width of the distal support surface 116 of
the first protrusions 114 is less than the width of the
piezoelectric elements 74. While the piezoelectric elements 74 are
shown in direct contact with the first tines 120, the spacing of
such first tines 120 need not be so close as to result in such a
direct contact. The spacing of the first tines 120 should be such
as to ensure that the first element side 74 completely covers the
distal support surface 116. As will be understood from the
discussion below, the distal support surface 116 will result in a
"footprint" that will facilitate the definition of the geometry of
the first peripheral portion 76 and the first exposed portion
78.
As seen in the view of FIG. 11, the piezoelectric element 74
defines a thickness and the protrusions 114 have a protrusion
height, and the first alignment comb 118 has a comb height as
defined by a height of the first tines 120. In this embodiment, the
comb height is greater than the protrusion height but less than the
sum of the thickness and the protrusion height. This results in the
piezoelectric elements 74 being raised in comparison to the first
tines 120.
Referring now to FIG. 12, a second alignment comb 122 may be
provided. The second alignment comb 122 includes a plurality of
second tines 124. The act of positioning further includes using the
second alignment comb 122 to position the piezoelectric elements 74
with respect to the first fixture 110. The piezoelectric elements
74 are positioned between respective ones of the second tines 124.
The second alignment comb 122 is positioned with the second tines
124 being oriented approximately orthogonally relative to the first
tines 120. As mentioned above, the piezoelectric elements 74 are
raised in comparison to the first tines 120 as shown in FIG. 11.
This allows the second tines 124 to engage the piezoelectric
elements 74 when the second alignment comb 122 is positioned atop
the first alignment comb 122.
FIG. 13 is a cross-sectional view as seen along axis 13-13 of FIG.
12. As can be seen, the length of the distal support surface 116 of
the first protrusions 114 is less than the length of the
piezoelectric elements 74. While the piezoelectric elements 74 are
shown in direct contact with the second tines 124, the spacing of
such second tines 124 need not be so close as to result in such a
direct contact. The spacing of the second tines 124 should be such
as to ensure that the first element side 74 completely covers the
distal support surface 116. As will be understood from the
discussion below, the distal support surface 116 will result in a
"footprint" that will facilitate the definition of the geometry of
the first peripheral portion 76 and the first exposed portion
78.
Referring now to FIG. 14, a second fixture 126 may be provided. The
method may further include providing the second fixture 126 that
includes a fixture base 128 and a plurality of protrusions 130
extending from the fixture base 128. Each protrusion 130 includes a
distal support surface 132 that is approximately the same size as a
second exposed portion 88 of a respective one of the second element
sides 84. Next, the method may further include positioning each of
the piezoelectric elements 74 upon a respective distal support
surface 132 of the second fixture 126 with the respective second
exposed portion 88 of a respective second element side 84 upon the
distal support surface 132. In this regard, as indicted by the
motion arrow indicator in FIG. 14, the second fixture 126 is then
flipped over and positioned upon the piezoelectric elements 74 as
shown in FIG. 15. Next, the method may further include affixing the
first and second fixtures 110, 126 relative to each other. As shown
in FIG. 16, this may be accomplished through the use of clamps 134
for example.
As shown in FIG. 17, the method may further include removing the
first and second alignment combs 118, 122. The clamps 134 maintain
the piezoelectric elements 74 between the first and second fixtures
110, 126. FIG. 18 is a cross-sectional view of the first and second
fixtures 110, 118 and the piezoelectric elements 74 as seen along
axis 18-18 of FIG. 17. FIG. 19 is a perspective view from another
angle of the first and second fixtures 110, 118 and the
piezoelectric elements of FIG. 17.
The act of forming the encapsulation layer 82 may then proceed
without the presence of the first and second alignment combs 118,
122 while the piezoelectric elements 74 are positioned between the
affixed first and second fixtures 110, 118. In this regard, the
first and second fixtures 110, 118 and the piezoelectric elements
74 may be exposed to a chemical bath or other deposition
environment for application of the encapsulation layer 82 upon the
piezoelectric elements 74. Referring now to FIG. 20, there is
depicted a view similar to that of FIG. 18, however, after the
application of the encapsulation layer 82 to the piezoelectric
elements 74. The distal support surfaces 116, 132 are utilized to
mask the first and second exposed portions 78, 88 from being
exposed to encapsulation material when applying the encapsulation
layer 82.
After the encapsulation, each of the piezoelectric elements 74 is
removed from the first and second fixtures 110, 118 as it is now
incorporated in a completed microactuator 60. The first and second
fixtures 110, 118 may be formed of any variety of materials, such
as steel or plastic. In addition, the surfaces of the first and
second fixtures 110, 118 may have a solid or liquid coated surface,
such as a polytetrafluoroethylene coating, to facilitate release of
the microactuators 60 upon completion.
According to yet another aspect of the invention, there is provided
an apparatus 136 for manufacturing a plurality of piezoelectric
microactuators (such as microactuator 60). Each microactuator is
for use in a disk drive (such as disk drive 10). The apparatus 136
includes the first fixture 110, the first alignment comb 118, and
the second alignment comb 122 as discussed above. In addition, the
apparatus 136 may further include the second fixture 126, also as
discussed above.
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